This is the boss. No calculator, and one declared convention: on this paper $2\pi = 6$. That is a 4.5% lie, said out loud, and it is the same move as rounding $g$ to 10 — every line then lands on a whole number and the chain stays in your head. What is being examined here is the chain, not the fourth digit. In the real world you carry 6.283; at a whiteboard, in front of a colleague, you carry 6.

One flywheel, read end to end, and every answer feeds the next: the nameplate rpm becomes $\omega$, the disk's mass and radius become $I$, the two together become the energy banked, and the run-up time turns that energy into the power the drive had to find. Write each line down as you go — one slip at the top rolls all the way to the invoice.

Then one last shaft question, because the number a machine designer actually needs is never the power. 5★ under par here is the chapter crown. Clock in.